Nearly perfect absorption of solar energy by coherent of electric and magnetic polaritons

Abstract

Photothermal conversion applications of solar energy are attracting more and more interests nowadays, and perfect absorption of solar energy by metamaterials is a key point for such a phenomenon. In the present study, we propose a nearly perfect solar absorber with double nested rings respectively made of platinum (Pt) and nickel (Ni) periodically arranged on a gold substrate. We theoretically and numerically discuss the underlying mechanisms of the optical properties for such a multi-materials absorber submerged in water by using the finite difference time domain (FDTD) method. The effects of material composition, height and radius of the nano-rings, the thickness of the gold substrate and alumina dielectric layer on the optical property of our proposed absorber are numerically analyzed. The absorptance of such a multi-materials absorber is higher than 96% in the whole wavelength range of 300–2400 nm, which accounts for almost the whole solar spectrum. Moreover, the solar absorber is insensitive to polarization while slightly sensitive to the incident angle of the light. Our solar absorber provides a new approach for the solar energy harvesting and photothermal conversion applications in water, such as solar vapor generation, sterilization, and so on.